In: Biology
Propose a 20 amino acid sequence for an amphipathic beta-hairpin strand.
The topology of a β-sheet describes the order of hydrogen-bonded β-strands along the backbone...Large aromatic residues (tyrosine, phenylalanine, tryptophan) and β-branched amino acids (threonine, valine, isoleucine) are favored to be found in β-strands in the middle of β-sheets.There are two residues per repeat unit which gives the beta-strand a 7 Angstrom pitch
There are two types of beta sheets,one is parallel beta sheet and the second one is anti parallel beta sheeet. Parallel beta sheets are chains of polypeptides, which run in the same direction. Anti-parallel beta sheets are chains of polypeptides which run in opposite directions to each other.Within a β sheet, as within an α-helix, all possible backbone hydrogen bonds are formed. In both parallel and antiparallel β sheet, the side groups along each strand alternate above and below the sheet, while side groups opposite one another on neighboring strands extend to the same side of the sheet and are quite close together.
Proline and Glycine are frequently found in beta turns, proline because its cyclic structure is ideally suited for the beta turn, and glycine because, with the smallest side chain of all the amino acids, it is the most sterically flexible..
Ile-Leu-Val-Leu Val-Ala-Thr-Gly-Ile Ala-Ile-Ala-Val, Ala-Ile-Leu-Ile-Ala, Ser-Thr-His-Val-Ser,